The close down pop elimination system (i.e. pop elimination in an audio amplification system) can be a central element of an audio power conversion system.
Most audio power converters are based on a PWM (Pulse-width modulation) modulator (digital modulator or analogue modulator) that converts a pulse-code-modulated signal (PCM) received from a source such as a CD-player, or an analogue signal preceded by a D/A converter, to for instance a pulse-width-modulated signal.
The output signal of the modulator is fed to a power stage where it is amplified. A typical power converter includes a switching power conversion stage, a filter and an analogue control system.
At close-down of the audio power conversion system, a general problem is the presence of an audible signal at the output of the system even though there is no input signal applied to the audio power conversion system. The signal at the output at close-down is called pop. A contributing source to the pop can be energy stored in the demodulation filter.
Another contributing source of the close-down pop can be non-controllable conduction of the MOSFETs at close-down which depends on the timing of the power stage.
WO 2008072212 describes a system with an added extra power stage.
US 20060182266 describes a system with charging of a DC block capacitor, which system is not for minimizing close-down pop in other types of systems.
There is therefore a need for an improved system and method for minimizing the close-down pop often present in audio power conversion systems.